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Single Conductor Woes... #163223 05/04/07 07:02 AM
Joined: May 2007
Posts: 7
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oldguy_46 Offline OP
New Member
I've been an industrial elecrician in Canada for many years and I am well aware of the sheath voltage issues with single conductor metal sheathed cables...and the preventive measures used to make things safer. I was recently questioned on using "one conductor only" in an NMD 14-2 cable in a house. I'm embarrased to say that I've never heard that this was not allowed. I can find a number of references to it when googling, and it appears it may be in the NEC. Can anyone tell me if this is a well known rule among all electrical contractors in the US...and if any Canadians are watching...is this in our CEC somewhere...specifically for residential wiring? Never too old to learn. sleep Thanks!!

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Re: Single Conductor Woes... [Re: oldguy_46] #163228 05/04/07 09:00 AM
Joined: Jan 2003
Posts: 174
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bigrockk Offline
Member
Hello "old guy" and welcome to ECN.
Just a couple of questions first, was your installation condemned by an inspector? and could you be more specific on your application of the cable.
It would be helpful to know why you were using just one conductor and what the application was.
I do mostly industrial myself so I know it is easy to fall behind on the resi stuff. This website is a great place to help you keep up.
If you scroll down the "Forums" page you will see a link for a thread that deals with "Canadian Electrical Code Topics"

Re: Single Conductor Woes... [Re: bigrockk] #163232 05/04/07 10:49 AM
Joined: Jun 2006
Posts: 613
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mikesh Offline
Member
In loomex you cannot just use 1 conductor as the bonding conductor has to be connected too. I am guessing you ran a 3 way switch and just used 2 X 2 wire loomex to accomplish this? I shows a lack of planning but I cannot see it as a violation. The unused conductor will have a voltage on it but I cannot see it will carry current or present a hazard as long as the unused ends are capped off.

Re: Single Conductor Woes... [Re: mikesh] #163257 05/04/07 08:37 PM
Joined: May 2007
Posts: 7
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oldguy_46 Offline OP
New Member
Hello bigrockk and mikesh. Thanks for replying. Mikesh...yes, sorry...the ground wire is being used too. Let me explain how this came up...I was trained as a construction electrician in the 70s and worked at that for several years before moving to industrial. I'm not sure I have ever done this myself, but suggested it to someone in the U.S. who basically freaked out totally trying to get me banned from the planet. My example was similar to adding a second 4-way switch by running 2 x 2 wire NMD from an existing 4-way to the new 4-way (not extedning the neutral). Yes...it will always be the case that current will be flowing in only one conductor in each cable...which is obviously viewed by some as a major issue. I have had quite a few CSA and code courses through the years and, other than the obvious problems in large metal sheathed single conductor cable installations...I have never heard of this...and that bothers me. The US people are using phrases like "this will kill someone quickly" and "this is burning down houses". I am wondering if this is actually in the CEC for residential wiring...and how long it has been a rule...and how long it has been common knowledge among contractors in Canada? Any info is appreciated. You are never too old to learn. Thanks guys, eh?

Re: Single Conductor Woes... [Re: oldguy_46] #163261 05/04/07 09:45 PM
Joined: Mar 2005
Posts: 212
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Gregtaylor Offline
Member
Someone with no real understanding of the code or theory will jump all over the things they don't understand every time. It's a control circuit and it doesn't require the grounded conductor to be run along with it and it's not burning down houses or killing people.
How do they explain the working of a romex, er, loomex, switch loop? True, the groundING conductor cannot be ignored, but that's a different issue.

Re: Single Conductor Woes... [Re: oldguy_46] #163271 05/05/07 05:31 AM
Joined: May 2007
Posts: 3
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RonS Offline
New Member
oldguy,
Sounds like a simple two-wire travler. Not uncommom in our area and approved by the local AHJ. No neutral or grounded conductor required between the three ways and four ways as long as the switch leg end and power end are supplied by the same circuit. Among the big residential ropers in our area this type of installation is used to save on 3-wire.

Re: Single Conductor Woes... [Re: RonS] #163318 05/06/07 09:48 AM
Joined: May 2007
Posts: 7
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oldguy_46 Offline OP
New Member
Thanks RonS and GregTaylor. I am starting to feel better. Let me run another example of this past you guys for comment if you don't mind. [img]http://www.flickr.com/photos/8155033@N04/486509925/[/img]

Any references to this kind of thing in code (NEC or CEC) or anywhere else would be greatly appreciated...to get this old guy "up to speed" where necessary. Thanks so much!!

Re: Single Conductor Woes... [Re: oldguy_46] #163319 05/06/07 10:27 AM
Joined: Mar 2005
Posts: 399
A
Alan Nadon Offline
Member
Old Guy Don't know the Canadian rules but, your installation is a violation in the U.S. The NEC 2002 section 300.3 (B) requires ALL conductors of the same circuit to be in the same raceway or cable. There are exceptions but your switch circuit doesn't fit them.
Alan--
Old guy...I'm 64 and still learning.


Alan--
If it was easy, anyone could do it.
Re: Single Conductor Woes... [Re: Alan Nadon] #163321 05/06/07 11:04 AM
Joined: Feb 2003
Posts: 231
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RobbieD Offline
Member
CEC 12-106 (1)

Wher a multi-conductor cable is used, all conductors of a circuit shall be contained in the same multi-conductor cable except that, where necessary to run conductors in parallel due to capacity of an alternating current circuit, additional cables shall be permitted to be used provided that any one such cable includes an equal number of conductors from each phase and neutral and shall be in accordance with Rule 12-108.

I know that the intent for this rule was for enabling the cancelling out of currents induced in metal sheath cables and that is not a problem here. I don't see a problem here because you are not really running the cables in parallel because it is a countinuous control circuit for the lights.

Re: Single Conductor Woes... [Re: RobbieD] #163329 05/06/07 03:52 PM
Joined: May 2007
Posts: 7
O
oldguy_46 Offline OP
New Member
Thanks for the replies...I see now also that a reference was added to the 1998 CEC mentioning inductive reactance and single conductors (although it refers to 1/0 cu / al or larger. I'm still not clear on #1 - How I never learned this in all these years, #2 - When this inductance issue became well known, and #3 - In residential #14 - 15A circuits wirred with NMD...how this is killing people and burning down houses? As we all know, a lot of things in the code are for simple, almost silly, things...and I am just trying to get a feel for how important this really one really is...all code aside. Thanks again! If anyone knows any more about this, please reply.

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